Intra-rat handover for next generation system

ABSTRACT

A method of an access and mobility function (AMF) for state management in a wireless communication system is provided. The method comprises determining a state of at least one state machine, receiving, from a target access network (AN), an N2 path switch request message based on the state of the at least one state machine, transmitting, to a session management function (SMF), an N11 message, and transmitting, to the target AN, an N2 path switch request acknowledgement (Ack) message when receiving an N11 Ack message, from the SMF, corresponding to the N11 message, wherein the target AN transmits a release resource message to a source AN when the target AN receives the N2 path switch request Ack message.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/443,344, filed on Jan. 6, 2017; U.S. ProvisionalPatent Application Ser. No. 62/443,868, filed on Jan. 9, 2017; U.S.Provisional Patent Application Ser. No. 62/445,074, filed on Jan. 11,2017; U.S. Provisional Patent Application Ser. No. 62/455,638, filed onFeb. 7, 2017; and U.S. Provisional Patent Application Ser. No.62/455,629, filed on Feb. 7, 2017. The content of the above-identifiedpatent document is incorporated herein by reference.

TECHNICAL FIELD

The present application relates generally to mobility managementoperation for next generation system. More specifically, this disclosurerelates to mobility, connection, and session management for nextgeneration systems.

BACKGROUND

5th generation (5G) mobile communications, initial commercialization ofwhich is expected around 2020, is recently gathering increased momentumwith all the worldwide technical activities on the various candidatetechnologies from industry and academia. The candidate enablers for the5G mobile communications include massive antenna technologies, fromlegacy cellular frequency bands up to high frequencies, to providebeamforming gain and support increased capacity, new waveform (e.g., anew radio access technology (RAT)) to flexibly accommodate variousservices/applications with different requirements, new multiple accessschemes to support massive connections, and so on. Existing cellularnetworks were not designed for supporting Internet of Things (IoT). LTEhas been designed from grounds up to provide efficient mobile broadbanddata communications. One of the important requirement supported LTE,UMTS/HSPA and GSM/GPRS is to support full mobility. Due to thisrequirement, the mobile is required to be paged in larger location areaanytime it goes to idle mode and receives terminating packets from thenetwork. Next generation wireless standards (e.g., 3GPP SA2) startedworking on the architecture standards. User management is a criticalpiece of this work. This includes how user plane is selected by thecontrol plane, how it is managed throughout the session, impact on theuser plane when multiple user planes are used for the same session etc.It includes details involving creation, modification and release of theuser plane. Modification involves mainly relocation of the UPF itselfand also relocation of the different functions of the UPF when multipleUPFs are used for traffic transmission to same or different datanetworks.

SUMMARY

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesbeyond 4th-Generation (4G) communication system such as long termevolution (LTE). Embodiments of the present disclosure provide multipleservices in advanced communication systems.

In one embodiment, an access and mobility function (AMF) for statemanagement in a wireless communication system is provided. The AMFcomprises a processor configured to determine a state of at least onestate machine, and a transceiver configured to receive, from a targetaccess network (AN), an N2 path switch request message based on thestate of the at least one state machine transmit, to a sessionmanagement function (SMF), an N11 message; and transmit, to the targetAN, an N2 path switch request acknowledgement (Ack) message whenreceiving an N11 Ack message, from the SMF, corresponding to the N11message, wherein the target AN transmits a release resource message to asource AN when the target AN receives the N2 path switch request Ackmessage.

In another embodiment, a method of an access and mobility function (AMF)for state management in a wireless communication system is provided. Themethod comprises determining a state of at least one state machine,receiving, from a target access network (AN), an N2 path switch requestmessage based on the state of the at least one state machine,transmitting, to a session management function (SMF), an N11 message,transmitting, to the target AN, an N2 path switch requestacknowledgement (Ack) message when receiving an N11 Ack message, fromthe SMF, corresponding to the N11 message, wherein the target ANtransmits a release resource message to a source AN when the target ANreceives the N2 path switch request Ack message.

In yet another embodiment, a non-transitory computer readable mediumcomprising instructions, that when executed by at least one processor,perform a method is provided. The non-transitory computer readablemedium comprises determining a state of at least one state machine,receiving, from a target access network (AN), an N2 path switch requestmessage based on the state of the at least one state machine,transmitting, to a session management function (SMF), an N11 message,and transmitting, to the target AN, an N2 path switch requestacknowledgement (Ack) message when receiving an N11 Ack message, fromthe SMF, corresponding to the N11 message, wherein the target ANtransmits a release resource message to a source AN when the target ANreceives the N2 path switch request Ack message.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout the present disclosure. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNB according to embodiments of thepresent disclosure;

FIG. 3 illustrates an example UE according to embodiments of the presentdisclosure;

FIG. 4 illustrates an example Xn based handover without UPF relocationaccording to embodiments of the present disclosure;

FIG. 5 illustrates an example Xn based handover with UPF relocationaccording to embodiments of the present disclosure;

FIG. 6 illustrates an example NSM state transition at UE according toembodiments of the present disclosure;

FIG. 7 illustrates an example NMM state transition according toembodiments of the present disclosure;

FIG. 8 illustrates an example NCM state transition according toembodiments of the present disclosure

FIG. 9 illustrates an example relation between NSM, NCM, and NMM statesat the UE according to embodiments of the present disclosure;

FIG. 10 illustrates an example relation between NSM, NCM, and NMM statesat the AMF according to embodiments of the present disclosure;

FIG. 11 illustrates an example user plane connectivity according toembodiments of the present disclosure;

FIG. 12 illustrates an example N4 session establishment procedureaccording to embodiments of the present disclosure;

FIG. 13 illustrates an example N4 session modification procedureaccording to embodiments of the present disclosure;

FIG. 14 illustrates an example N4 session termination procedureaccording to embodiments of the present disclosure;

FIG. 15 illustrates an example N4 session establishment serviceaccording to embodiments of the present disclosure;

FIG. 16 illustrates an example N4 session modification service accordingto embodiments of the present disclosure; and

FIG. 17 illustrates an example N4 session termination service accordingto embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 through FIG. 17, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents are hereby incorporated by reference into thepresent disclosure as if fully set forth herein: 3GPP TS 23.501 v.1.6,“3rd Generation Partnership Project; Technical Specification GroupServices and System Aspects; System Architecture for the 5G System,” and3GPP TS 23.502 v.1.3, “3rd Generation Partnership Project; TechnicalSpecification Group Services and System Aspects; Procedures for the 5GSystem.”

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.”

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

FIGS. 1-3 below describe various embodiments implemented in wirelesscommunications systems and with the use of orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA) communication techniques. The descriptions of FIGS. 1-3 are notmeant to imply physical or architectural limitations to the manner inwhich different embodiments may be implemented. Different embodiments ofthe present disclosure may be implemented in any suitably-arrangedcommunications system.

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure. The embodiment of the wireless network shownin FIG. 1 is for illustration only. Other embodiments of the wirelessnetwork 100 could be used without departing from the scope of thisdisclosure.

As shown in FIG. 1, the wireless network includes an eNB 101, an eNB102, and an eNB 103. The eNB 101 communicates with the eNB 102 and theeNB 103. The eNB 101 also communicates with at least one network 130,such as the Internet, a proprietary Internet Protocol (IP) network, orother data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point(AP), or other wirelessly enabled devices. Base stations may providewireless access in accordance with one or more wireless communicationprotocols, e.g., 5G 3GPP new radio interface/access (NR), long termevolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS”and “TRP” are used interchangeably in the present disclosure to refer tonetwork infrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, the term “userequipment” or “UE” can refer to any component such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” “receivepoint,” or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in the present disclosure to refer toremote wireless equipment that wirelessly accesses a BS, whether the UEis a mobile device (such as a mobile telephone or smartphone) or isnormally considered a stationary device (such as a desktop computer orvending machine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programming, or a combination thereof, for efficientinter-RAT handover operation in advanced wireless communication system.In certain embodiments, and one or more of the eNBs 101-103 includescircuitry, programming, or a combination thereof, for efficientinter-RAT handover operation in an advanced wireless communicationsystem.

Although FIG. 1 illustrates one example of a wireless network, variouschanges may be made to FIG. 1. For example, the wireless network couldinclude any number of eNBs and any number of UEs in any suitablearrangement. Also, the eNB 101 could communicate directly with anynumber of UEs and provide those UEs with wireless broadband access tothe network 130. Similarly, each eNB 102-103 could communicate directlywith the network 130 and provide UEs with direct wireless broadbandaccess to the network 130. Further, the eNBs 101, 102, and/or 103 couldprovide access to other or additional external networks, such asexternal telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for an inter-RAThandover operation and state transition. The processor 340 can move datainto or out of the memory 360 as required by an executing process. Insome embodiments, the processor 340 is configured to execute theapplications 362 based on the OS 361 or in response to signals receivedfrom eNBs or an operator. The processor 340 is also coupled to the I/Ointerface 345, which provides the UE 116 with the ability to connect toother devices, such as laptop computers and handheld computers. The I/Ointerface 345 is the communication path between these accessories andthe processor 340.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

Xn interface referred in the present disclosure may a control and userplane interface defined between two gNodeBs (gNBs).

In some embodiments, an Xn based handover without user plane functionrelocation may be considered. This procedure is used to hand over a UEfrom a source (radio) access network (R)AN) to target (R)AN using Xninterface when the access and mobility management function (AMF) isunchanged and the session management function (SMF) decides to keep theexisting user plane function (UPF). The UPF referred in this clause isthe UPF which terminates N3 interface in the 5G next generation core(NGC). The presence of internet protocol (IP) connectivity between thesource UPF and target UPF is assumed.

FIG. 4 illustrates an example Xn based handover without UPF relocation400 according to embodiments of the present disclosure. An embodiment ofthe Xn based handover without UPF relocation 400 shown in FIG. 4 is forillustration only. One or more of the components illustrated in FIG. 4can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As illustrated in FIG. 4, at step 1, the target (R)AN sends an N2 pathswitch request message to an AMF to inform that the UE has moved to anew target cell and a list of bearers to be switched. Depending on thetype of target cell, the target (R)AN includes appropriate informationin this message. At step 2, the AMF sends an N11 message to one or moreSMFs currently serving the UE which includes the list of bearers to beswitched. At step 3, upon receipt of the N11 message, the SMF determinesthat the existing UPF can continue to serve the UE. Each SMF maintainsthe corresponding list of the bearers from the UE context. If some ofthese bearers are not accepted by the target (R)AN, the SMF initiatesrelease of those bearers at that time. For all accepted bearers, the SMFsends an N4 session modification request ((R)AN address, tunnelidentifiers for downlink user plane) message. At step 4, the UPF mayreturn an N4 session modification response (e.g., tunnel identifiers foruplink traffic) message to the SMF. At step 5, in order to assist thereordering function in the target (R)AN, the UPF may send one or more“end marker” packets on the old path immediately after switching thepath. The UPF starts sending downlink packets to the target (R)AN. Atstep 6, this step can occur anytime after receipt of step 4 at the SMF.Each SMF sends an N11 message response (e.g., tunnel identifiers foruplink traffic) to the AMF. At step 7, the AMF aggregates N11 messageresponses received from SMF(s) along with the list of bearers failed toswitch. The AMF confirms the N2 path switch request message by sendingN2 path switch request Ack (e.g., UPF address, tunnel identifiers foruplink traffic) message to the target (R)AN. If none of the requestedbearers have been switched successfully, the AMF may send an N2 pathswitch request failure message to the target (R)AN. At step 8, bysending a release resources message to the source (R)AN, the target(R)AN confirms success of the handover. It then triggers the release ofresources with the Source (R)AN.

In some embodiments, an Xn based handover with user plane functionrelocation may be considered. This procedure is used to hand over a UEfrom a source (R)AN to a target (R)AN using Xn when the AMF and SMF areunchanged and the SMF decides that the source UPF is to be located. Thesource UPF referred in this clause is the UPF which terminates N3interface in the NGC. The presence of IP connectivity between the sourceUPF and Source (R)AN, and between the target UPF and target (R)AN, isassumed.

FIG. 5 illustrates an example Xn based handover with UPF relocation 500according to embodiments of the present disclosure. An embodiment of thenetwork slicing 500 shown in FIG. 5 is for illustration only. One ormore of the components illustrated in FIG. 5 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As illustrated in FIG. 5, the steps 1 and 2 are the same as discussed inthe aforementioned embodiment (e.g., Xn based handover without userplane function relocation) of the present disclosure. As illustrated inFIG. 5, at step 3, the SMF determines that the source UPF needs to berelocated based on UPF selection criteria and selects a new target UPF.Each SMF maintains the corresponding list of the bearers from the UEcontexts. If some of these bearers are not accepted by the target (R)AN,the SMF initiates release of those bearers at that time. All acceptedbearers are included in an N4 session establishment request message sentto the target UPF. Target UPF IP address assignment, and allocation ofdownlink and uplink tunnel identifiers are performed by the SMF. An N4session establishment request (e.g., target (R)AN address, uplink anddownlink tunnel identifiers) message is sent to the target UPF. At step4, the target UPF sends an N4 session establishment response message tothe SMF. The SMF starts a timer, to be used in step 10. At this point,the target UPF starts sending downlink packets to the target (R)AN usingthe newly received address and tunnel identifiers. At step 5, if the PDUsession anchor function is not collocated with the target UPF, the SMFmay initiate N4 session modification procedure with the UPF having PDUsession anchor function. At step 6, the UPF having PDU session anchorfunction responds with the N4 session modification response. At step 7,each SMF sends a N11 message response (e.g., target (R)AN address,tunnel identifiers for uplink traffic) to the AMF. At step 8, the AMFaggregates N11 message responses received from SMF(s) along with thelist of bearers failed to switch. The AMF confirms the N2 path switchrequest message with the N2 path switch request Ack (e.g., target UPFaddress, tunnel identifiers for uplink traffic) message. If none of therequested bearers have been switched successfully. In this case, the AMFmay send an N2 path switch request failure message to the target (R)AN.At step 9, by sending a release resources message to the source (R)AN,the target (R)AN confirms success of the handover and triggers therelease of resources with the source (R)AN. At step 10, once the timerhas expired after step 4, the SMF initiates source UPF release procedureby sending an N4 session termination request (release cause). At step11, the source UPF acknowledges with an N4 session termination responsemessage to confirm the release of resources.

The NextGen session management (NSM) describes the signaling and bearerconnectivity between the UE and the NextGen core network (CN), i.e.signaling connectivity with the SMF (N2) and bearer connectivity withthe UPF (N3). In general, the NSM and NextGen mobility management (NMM)and NextGen connection management (NCM) states are independent of eachother.

The NSM states are supported independently of the access networktechnology the UE may be using. These states are maintained at the UE.The following three states are defined for connectivity to a datanetworks(s), regardless of the number of PDU sessions the UE hasestablished to a given data network: NSM-IDLE; NSM-READY; andNSM-CONNECTED

A UE is in NSM-IDLE state when there is no signaling connection existbetween the UE and NextGen CN and also there is no UE context availableat the NextGen access network. The RRC connection has not beenestablished at that time and hence the UE remains in RRC-IDLE state.

A UE is in NSM-READY state when there is a signaling connection exist(N1 and N2) between the UE and NextGen CN but there is no PDU sessionexist at that time. The UE context is also available at the NextGenAccess Network. The RRC connection has not been established at that timeand hence the UE remains in RRC-IDLE state.

For a UE in the NSM-CONNECTED state, there exists a signaling connectionand at least one bearer connection between the UE and the NextGen CN.Since N2 terminates at the AMF, messages intended for the SMF areterminated via AMF to the SMF. In this state, the location of the UE isknown and the mobility of the UE is handled by the handover procedureand tracking area update procedures. There may be at least one sessionexist between the UE and NextGen CN. The RRC state may be RRC-CONNECTEDat that time for all active PDU sessions while it is RRC-INACTIVE forall inactive PDU sessions.

The UE may enter the NSM-IDLE state when the last PDU session or (adefault PDU session in case if PDU session was established along withAttach procedure) to the SMF is released or broken. This release orfailure is explicitly indicated by the access node to the UE or detectedby the UE.

FIG. 6 illustrates an example NSM state transition 600 at UE accordingto embodiments of the present disclosure. An embodiment of the NSM statetransition 600 shown in FIG. 6 is for illustration only. One or more ofthe components illustrated in FIG. 6 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The NSM state transitions from NSM-IDLE to NSM-CONNECTED at the UE mayoccur once it establishes a PDU session. The RRC connection isestablished at that time. The NSM state remains NSM-CONNECTED forrequest of additional PDU sessions at both UE and the SMF. Once the lastPDU session is release, the NSM state may transition to NSM-IDLE at theUE.

There may be some special cases where the UE requests the PDU sessionestablishment at the same time as the attach. At that time also the UEstate may transit to NSM-CONNECTED from NSM-IDLE and remain connected incase if additional PDU sessions are requested. The release of thedefault PDU session may transit to the NSM state at UE.

The NMM states describe the mobility management states that result fromthe mobility management procedures such as attach and tracking areaupdate procedures. These states are maintained at the UE and also at theAMF in the NextGen CN. The following are the two states considered inthe present disclosure. In one example of EMM-DEREGISTERED state, theNMM context in AMF holds no valid location or routing information forthe UE. The UE is not reachable by an AMF, as the UE location is notknown. Some UE context mainly related to security can still be stored inthe UE and AMF. In another example of EMM-REGISTERED state, the UElocation is known in the AMF to at least an accuracy of the trackingarea list allocated to that UE. The UE also has security context setwith the N1 and N2 signaling connectivity available with the AMF.

FIG. 7 illustrates an example NMM state transition 700 according toembodiments of the present disclosure. An embodiment of the NMM statetransition 700 shown in FIG. 7 is for illustration only. One or more ofthe components illustrated in FIG. 7 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The UE and AMF may enter in the NMM-REGISTERED state completion ofattach procedure or tracking area update and they may enter in theNMM-IDLE state once UE is detached. At that time, the AN may clean theUE context for that UE.

The NCM states describe the signaling connectivity between the UE andthe NextGen CN. These states are maintained at the UE and the AMF. Thereare two ECM states described in the present disclosures. In one exampleof ECM-IDLE, there is no signaling connection between UE and NextGen CNexists, i.e. no N1 and N2 connections. Also, there exists no UE contextin the access network (AN) for the UE in the ECM-IDLE state. In yetanother example of ECM-CONNECTED, signaling connectivity between UE andNextGen exists from the UE and AMF perspective. RRC connection may notbe established and hence UE may remain in the RRC-IDLE state. Althoughthese is no N11 connectivity exist between the AMF and the SMF(s) andalso may not have N3 connectivity between the AN and UPF for that UE.

FIG. 8 illustrates an example NCM state transition 800 according toembodiments of the present disclosure. An embodiment of the NCM statetransition 800 shown in FIG. 8 is for illustration only. One or more ofthe components illustrated in FIG. 8 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The UE and AMF may enter in the NCM-CONNECTED state completion of attachprocedure and they may enter in the NCM-IDLE state once UE is detached.At that time, the AN may clean the UE context for that UE.

The NMM states are maintained at the UE and at the AMF in the NextGenCN. Similarly, the NSM states are maintained at the UE and at the AMF inNextGen CN. The relationship between the NSM states and the mobilitymanagement states is defined in such a way that the NSM states apply toany access network (AN) connected to the NextGen CN, including scenariosin which the UE supports no mobility.

FIG. 9 illustrates an example relation between NSM, NCM and NMM states900 at the UE according to embodiments of the present disclosure. Anembodiment of the relation between NSM, NCM and NMM states 900 shown inFIG. 9 is for illustration only. One or more of the componentsillustrated in FIG. 9 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The relation between the NSM states, NCM states and NMM states which aremaintained by the UE is shown in FIG. 9. In one example ofNMM-DEREGISTERED, NCM-IDLE, and NSM-IDLE, the UE may not be powered onor not attached to the NextGen CN. In this state, the AMF does not holdvalid location or routing information for the UE and hence UE is notreachable. There is no signaling connection exists between the UE andthe AMF/SMF.

In another example of NMM-REGISTERED, NCM-CONNECTED, and NSM-READY, theUE may enter the NMM-REGISTERED state by a successful registration withan Attach procedure. At that time, the RRC state at the UE may stillremain RRC-IDLE. The NextGen access network preserves the context of theUE. There is a signaling connections (N1 and N2) exists between the UEand the NextGen CN but there is no bearer connection exist (N3) sincethere is no active PDU session established at that time. In yet anotherexample of NMM-REGISTERED, NCM-CONNECTED, and NSM-CONNECTED, the UE isconnected to the NextGen CN by establishing signaling and bearerconnections. There are one or multiple PDU sessions being processed bythe SMF. The RRC state may be RRC-CONNECTED if the PDU session is activeat that time. Otherwise, the RRC state may be RRC-INACTIVE.

FIG. 10 illustrates an example relation between NSM, NCM and NMM states1000 at the AMF according to embodiments of the present disclosure. Anembodiment of the relation between NSM, NCM and NMM states 1000 shown inFIG. 10 is for illustration only. One or more of the componentsillustrated in FIG. 10 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The relation between the NMM states and NCM states which are maintainedby the AMF is shown in FIG. 10. In one example of NMM-DEREGISTERED andNCM-IDLE state, the AMF does not hold valid location or routinginformation for the UE and hence UE is not reachable. There is nosignaling connection exists between the UE and the AMF. In anotherexample of NMM-REGISTERED and NCM-CONNECTED state, the AMF enters theNMM-REGISTERED state by processing tracking area update procedure or anAttach procedure via NextGen access network. In this state, UE becomesreachable from the AMF perspective through the signaling connectivity.

The user plane function (UPF) selection may be performed by the sessionmanagement function (SMF) during the session establishment or when UPFrelocation is required. The selection may be done based on per PDUsession granularity where there is one tunnel per PDU session betweenaccess node (AN) and UPF in NextGen core network (CN) and between UPFs.All QoS classes of a session share the same outer IP header, but theencapsulation header identifies the PDU session and may carry QoSmarkings.

NextGen CN includes support of multi-homing UEs also support multipleconnection to the same or different data networks for supporting localservices and external services. From the routing perspective, thefollowing functions defined which may coexist with the UPF. In oneexample of uplink classifier function, uplink classifier function (UCF)normally resides at the UPF which serves as an N3 termination point. Itallows steering of local traffic and external traffic to theirrespective networks. It applies operator defined filtering rules anddetermines routing of the packets. The support of UCF is optional, butnecessary if the operator supports traffic to the local network. Theoperator may use configuration or policies to determine which packetflows are to be routed to/from the local network. Such configuration orpolicies are applied using uplink classification based on IP-5-tuplefiltering rules. For downlink, the operator configures the networkrouting such that only legitimate traffic from the local server may passvia the UPF local IP point of presence.

In another example of IP anchoring function, IP anchoring function (IAF)is a part of UPF that provides access to the external services andlocates in the more central location. It is responsible for UE IPaddress management. The support of the IAF is mandatory. In yet anotherexample of branching function, a branching function (BF) is enabled forsupporting multi-path/multi-homing PDU connections. It enables trafficfrom the UE to be split via multiple paths through multiple UPFs in theuplink direction. Similarly in the downlink direction, incoming trafficfrom multiple UPFs, is aggregated by this function prior to transmittingto the UE. This is a logical functional entity generally collocated withthe UPF which is an N3 termination point in order to supportmulti-path/multi-homing transmission capability.

FIG. 11 illustrates an example user plane connectivity 1100 according toembodiments of the present disclosure. An embodiment of the user planeconnectivity 1100 shown in FIG. 11 is for illustration only. One or moreof the components illustrated in FIG. 11 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

Only one host IP address that is centrally anchored may be assigned tothe UE. The UCF with the local IP point of presence examines destinationIP address and decides whether to transmit the PDU within a tunnel tothe external IP anchor or it may be transmitted to the local network.

The UE IP address management includes allocation and release of the UEIP address as well as renewal of the allocated IP address, whereapplicable. The UE IP address management may be performed by the SMF.The SMF may process the UE IP address management related messages,maintain the corresponding state information and provide the responsemessages to the UE. In case the UE IP address is obtained from theexternal DNN, additionally, the SMF may also send the allocation,renewal and release related request messages to the external DNN andmaintain the corresponding state information. The IAF may supportforwarding of the UE IP address management related messages to the SMF,when they are received via the user plane signaling from the UE or fromthe external PDN.

When SMF performs IPv4 address allocation via default bearer activationand release via PDN connection release, no special functionality isrequired from the IAF. For the other UE IP address managementmechanisms, the UE sends the IP address management related requestmessages via the user plane signaling. Hence the IAF is required toforward these request messages to the SMF for processing. Once theserequest messages are processed by the SMF, the SMF sends responsemessages to the UE via the user plane signaling. Hence the SMF isrequired to forward these response messages to the IAF so that it can berelayed it to the UE. Correspondingly, following functionality isrequired to be supported by the SMF and IAF.

In one example, for IPv6 default prefix management via IPv6 statelessaddress auto-configuration, the SMF may configure IAF to forward routersolicitation and neighbor solicitation messages from the UE to the SMF.The SMF may forward router advertisement and neighbor advertisementmessages to the IAF for relaying them to the UE.

In another example, for IPv6 parameter configuration via statelessDHCPv6, the SMF may configure IAF to forward all the DHCPv6 messagesfrom the UE to the SMF. The SMF may forward the DHCPv6 response messagesto the IAF for relaying them to the UE.

In yet another example, for IPv4 address management and parameterconfiguration DHCPv4, the SMF may configure IAF to forward all theDHCPv4 messages from the UE to the SMF. The SMF may forward the DHCPv4response messages to IAF for relaying them to the UE.

In yet another example, for IPv6 prefix management via IPv6 prefixdelegation, the SMF may configure IAF to forward all the DHCPv6 messagesfrom the UE to the SMF. The SMF may forward the DHCPv6 response messagesto IAF for relaying them to the UE.

The selection of the UPF is performed by the SMF by considering UPFdeployment scenarios such as centrally located UPF and distributed UPFlocated close to or at the access network site. The selection of the UPFmay also enable deployment of UPF with different capabilities, e.g. UPFssupporting no or a subset of optional functionalities. The UPFscapabilities may be signaled during the initial connection establishmentbetween the SMF and the UPF. The SMF may be made dynamically aware onthe UPF load and relative static capacity for which it has anestablished N4 session.

The exact set of parameters used for the selection mechanism isdeployment specific and controlled by the operator configuration, e.g.location information may be used for selecting UPF in some deploymentswhile may not be used in other deployments. For UPF selection, the SMFmay be able to consider the following parameters. In one example, theUPF's dynamic load is considered at the node level. In such example, theSMF may then derive the load at the APN level. In another example, theUPF's relative static capacity among UPFs supporting the same APN isconsidered. In yet another example, the UPF location available at theSMF is considered. In such example, the UPF selection function usesthese parameters based on SMF configuration to select a UPF close to theUE's point of attachment. In yet another example, the capability of theUPF and the functionality required for the particular UE session isconsidered. In yet another example, an appropriate UPF can be selectedby matching the functionality and features required for an UE (which canbe derived from the information such as APN, mapped UE Usage Type, UElocation information) or from the policy function (e.g. need to performDPI)) with the capabilities of the UPF so as to fulfil the service forthe UE. In yet another example, to enable APN-AMBR enforcement, whethera PDN connection already exists for the same UE and APN, in which casethe same UPF may be selected.

One of the main tasks of the N4 interface is to enable the SMF toinstruct the UPF about how to forward user data traffic. The followinguser plane forwarding scenarios are supported. In one example,forwarding of user-plane between UE and DDN is supported, includingmapping of tunneling between AN and UPF and between UPFs. In anotherexample, forwarding of user-plane packets from UE and SMF via UPF issupported. In such example, similarly, forwarding of packets from theexternal DDN and the SMF is supported. Example includes packets relatedto DHCPv4/v6, traffic subject to HTTP redirect etc. In yet anotherexample, forwarding of packets subject to buffering in the SMF issupported.

The SMF controls user-plane packet forwarding by providing traffichandling instructions to the UPF. The traffic handling instructionsinclude: packet detection information; and forwarding target andoperation information.

The packet detection information includes information which allows theUPF to identify the traffic that is subject to the forwarding treatmentdescribed by the forwarding target. The information may allow detectionon L3, L4, L7/application, bearer and DDN connection level. Theforwarding target and operation describes how the UPF may treat a packetthat matches the packet detection information. The details of theforwarding target and operation may depend on the scenario. Thefollowing forwarding functionality is required by the UPF: applyencapsulation, de-capsulation or both; forward the traffic to the SMF;and apply locally configured policy for traffic steering.

For forwarding between the SMF and UPF, the user plane packet isforwarded outside of the control protocol over N4 by encapsulating theuser-plane packet using a UP encapsulation protocol that allows thereceiving entity to identify which DDN Connection and possibly whichbearer the traffic belongs to.

In the direction from the SMF to UPF for forwarding towards the UE orDDN, the UP encapsulation protocol also may contain information thatallows the UPF to identify whether the UE or DDN is targeted. Thisapplies in the same way for traffic from the SMF to the UPF as well asfor traffic from the UPF to the SMF.

Buffering of the UE's data packets for the UE in idle or power savingmode is performed in SMF on a per UE session basis. When the UE moves toNCM-IDLE state, if the SMF decides to activate buffering, it may informthe UPF to stop sending data packets to the AN and start forwarding thedownlink data packets towards the SMF. When the UE transits to theNCM-CONNECTED state, the SMF may update the UPF via N4 interface withtunnel specific parameters. If there are buffered packets available andtheir buffering duration has not expired, the SMF may forward thosepackets to the UPF outside of the control plane signaling to relay themto the UE. These packets are then forwarded by the UPF to the AN.

N4 connectivity between the SMF and the UPF may exist prior toinitiation of the N4 session establishment procedure. As a part of PDUsession establishment, the UPF stores the N4 session context based onthe information provided by the SMF. This N4 session context comprisesof parameters required for managing bearers at the UPF. The SMF maymodify the N4 Session Context during the PDU session and later releaseit once the PDU session is released.

N4 session management procedures are used to control the functionalityof the UPF for a specific PDU session. N4 connectivity between the SMFand the UPF may exist prior to initiation of the N4 sessionestablishment procedure. N4 session management procedures include N4session establishment procedure, N4 session modification procedure andN4 session termination procedure. All of these procedures are initiatedby the SMF.

The following parameters are exchanged over the N4 interface between theSMF and UPF. This is not an exhaustive list but includes majority of theparameters needed to control different actions needed at the UPF; asession id; precedence (can be overall or per rule basis); bufferingstart/stop notification; packet detection rule (e.g., data networkinstance id, interface direction, UE IP address, local tunnel identifierand UPF address, SDF filter and application id); usage reporting rule(e.g., measurement key, reporting triggers, periodic measurementthreshold, volume measurement threshold, time measurement threshold,event measurement threshold, Inactivity detection time and Event basedreporting); forwarding action rule; reporting rule (e.g., measurementkey, reporting triggers, start time, end time, measurement information,time of last packet); and QoS enforcement rule (e.g., QoS enforcementrule correlation identifier, UL/DL gate status, maximum bitrate,guaranteed bitrate, transport level marking, extension header.

During PDU session establishment and UPF relocation procedures, the N4session establishment procedure is executed between SMF and UPF. Thisprocedure is used to create the initial N4 Session Context for the newPDU session at the UPF. The N4 Session Context comprises the parametersrequired for managing each bearer of the PDU session at the UPF and itis stored based on the session identifier.

FIG. 12 illustrates an example N4 session establishment procedure 1200according to embodiments of the present disclosure. An embodiment of theN4 session establishment procedure 1200 shown in FIG. 12 is forillustration only. One or more of the components illustrated in FIG. 12can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 12, at step 1, an SMF receives the trigger to establisha new connection from a peer network entity. At step 2, the SMF sends anN4 session establishment request message to the UPF that containsparameters/rules instructing actions for the UPF. This includesparameters listed in clause “parameters exchanged over N4” of thepresent disclosure. At step 3, the UPF creates an N4 Session Context andresponds with an N4 session establishment response message containinginformation that the UPF has to provide to the SMF in response to theinformation received.

The N4 session modification procedure is used to update the N4 sessioncontext of an existing connection of a PDU session at the UPF. The N4session modification procedure is executed between SMF and UPF wheneverparameters/rules related to existing connection of the PDU session haveto be modified.

FIG. 13 illustrates an example N4 session modification procedure 1300according to embodiments of the present disclosure. An embodiment of theN4 session modification procedure 1300 shown in FIG. 13 is forillustration only. One or more of the components illustrated in FIG. 13can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 13, at step 1, an SMF receives a trigger to modify theexisting connection of the PDU session from a peer network entity. Atstep 2, the SMF sends an N4 session modification request message to theUPF that contains the update for the parameters(s)/rule(s) instructingactions for the UPF. This includes one or more parameters listed inclause “parameters exchanged over N4” of the present disclosure. At step3, the UPF identifies the N4 Session Context to be modified based on thesession identifier. Then, the UPF updates the N4 Session Contextaccording to the information sent by the SMF. The UPF responds with anN4 session modification response message containing information that theUPF has to provide to the SMF.

FIG. 14 illustrates an example N4 session termination procedure 1400according to embodiments of the present disclosure. An embodiment of theN4 session termination procedure 1400 shown in FIG. 14 is forillustration only. One or more of the components illustrated in FIG. 14can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

The N4 session termination procedure is illustrated in FIG. 14. It isused to remove the N4 Session Context from the UPF. At step 1, an SMFreceives the trigger to terminate the existing connection for a PDUsession from a peer network entity. At step 2, the SMF sends an N4session termination request message to the UPF. At step 3, the UPFidentifies the N4 session context to be terminated based on the sessionidentifier and removes the N4 session context. The UPF responds with anN4 session termination response message containing information that theUPF has to be provided to the SMF.

In some embodiments of service description, the requestor queries theUPF to create N4 session context for a connection of a PDU session. Insome embodiments of input, session identifier and other parameters/ruleslisted in clause “parameters exchanged over N4” of the presentdisclosure. In some embodiments of output, N4 session context is createdto control each bearer connections associated with the PDU session

FIG. 15 illustrates an example N4 session establishment service 1500according to embodiments of the present disclosure. An embodiment of theN4 session establishment service 1500 shown in FIG. 15 is forillustration only. One or more of the components illustrated in FIG. 15can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 15, at step 1, a requestor sends an N4 sessionestablishment request (session identifier and other parameters/rules)message requesting the UPF to create N4 session context. At step 2, theUPF creates an N4 session context and responds with an N4 sessionestablishment response (session identifier, other parameters and controlinformation) message providing status of the N4 session establishmentresponse message's action based on the request.

FIG. 16 illustrates an example N4 session modification service 1600according to embodiments of the present disclosure. An embodiment of theN4 session modification service 1600 shown in FIG. 16 is forillustration only. One or more of the components illustrated in FIG. 16can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 16, at step 1, a requestor sends an N4 sessionmodification request (session identifier and other parameters/rules)message requesting the UPF to update existing N4 session context. Atstep 2, the UPF updates an N4 session context and responds with an N4Session modification response (session identifier and otherparameters/rules) message providing status of N4 Session modificationresponse message's action based on the request. In some embodiments ofservice description, the requestor queries the UPF to modify existing N4session context.

FIG. 17 illustrates an example N4 session termination service 1700according to embodiments of the present disclosure. An embodiment of theN4 session termination service 1700 shown in FIG. 17 is for illustrationonly. One or more of the components illustrated in FIG. 17 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

As shown in FIG. 17, at step 1, a requestor sends an N4 sessiontermination request message requesting the UPF to remove existing N4session context. At step 2, the UPF removes an N4 session context andresponds with an N4 session termination response (session identifier,status) message providing status of N4 session termination responsemessage's action.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. An access and mobility function (AMF) for statemanagement in a wireless communication system, the AMF comprising: aprocessor configured to determine a state of at least one state machine;and a transceiver configured to: receive, from a target access network(AN), an N2 path switch request message based on the state of the atleast one state machine; transmit, to a session management function(SMF), an N11 message; and transmit, to the target AN, an N2 path switchrequest acknowledgement (Ack) message when receiving an N11 Ack message,from the SMF, corresponding to the N11 message, wherein the target ANtransmits a release resource message to a source AN when the target ANreceives the N2 path switch request Ack message.
 2. The AMF of claim 1,wherein the SMF receives, from a user plane function (UPF), an N4session modification response message corresponding to an N4 sessionmodification request message that is transmitted to the UPF by the SMFwhen the SMF receives the N11 message from the AMF and decides to reusethe UPF.
 3. The AMF of claim 1, wherein the transceiver is furtherconfigured to transmit, to at least one SMF, the N11 message based on anumber of packet data unit (PDU) sessions associated with a userequipment (UE).
 4. The AMF of claim 1, wherein the SMF receives, from atarget UPF, an N4 session establishment response message correspondingto an N4 session establishment request message that is transmitted tothe target UPF by the SMF when the SMF receives the N11 message from theAMF and decides to use a new UPF as the target UPF.
 5. The AMF of claim2, wherein the SMF transmits the N4 session modification request messageto an anchor UPF when the SMF identifies at least two UPFs, the at leasttwo UPFs including the anchor UPF.
 6. The AMF of claim 1, where the SMFreceives, from a source UPF, an N4 session termination response messagecorresponding to an N4 session termination request message transmittedto the source UPF.
 7. The AMF of claim 1, wherein the at least one statemachine comprises: a mobility management state to complete at least oneof an attachment procedure or tracking area update procedure associatewith a user equipment (UE), the mobility management state including anNMM-DEREGISTERED state and an NMM-REGISTERED state; and a connectionmanagement state to complete an attachment procedure associated with theUE, the connection management state including an NCM-IDLE state and anNCM-CONNECTED state, and wherein a state machine of the UE issynchronized with the mobility management state and the connectionmanagement state, respectively.
 8. The AMF of the claim 7, wherein theat least one state machine further comprises a session management stateto complete a signaling connection and at least one bearer connectionassociated with the UE, the session management state including anNSM-IDLE state, an NSM-READY state, and an NSM-CONNECTED state andwherein: a state transition of the AMF from the NSM-IDLE state to theNSM-CONNECTED state is performed when a new PDU session is establishedupon receipt of a service request message from the UE to the AMF, theSMF being de-selected; a state transition of the UE from the NSM-READYstate to the NSM-CONNECTED state is performed when a first PDU sessionestablishment request message is transmitted to the AMF from the UE, theNSM-CONNECTED state lasting until a last PDU session released; and astate transition of the UE from the NSM-IDLE state to the NSM-READYstate is performed when the UE attaches to a network.
 9. The AMF of theclaim 8, wherein the NMM-REGISTERED state, the NCM-CONNECTED state, andthe NSM-CONNECTED state comprise a radio resource control (RRC) stateincluding an RRC-CONNECTED state and an RRC-IDLE state based on a numberof PDU sessions associated with a UE that comprises the RRC-CONNECTEDstate, the RRC-IDLE state, and an RRC-INACTIVE state.
 10. A method of anaccess and mobility function (AMF) for state management in a wirelesscommunication system, the method comprising: determining a state of atleast one state machine; receiving, from a target access network (AN),an N2 path switch request message based on the state of the at least onestate machine; transmitting, to a session management function (SMF), anN11 message; and transmitting, to the target AN, an N2 path switchrequest acknowledgement (Ack) message when receiving an N11 Ack message,from the SMF, corresponding to the N11 message, wherein the target ANtransmits a release resource message to a source AN when the target ANreceives the N2 path switch request Ack message.
 11. The method of claim10, wherein the SMF receives, from a user plane function (UPF), an N4session modification response message corresponding to an N4 sessionmodification request message that is transmitted to the UPF by the SMFwhen the SMF receives the N11 message from the AMF and decides to reusethe UPF.
 12. The method of claim 10, further comprising transmitting, toat least one SMF, the N11 message based on a number of packet data unit(PDU) sessions associated with a user equipment (UE).
 13. The method ofclaim 10, wherein the SMF receives, from a target UPF, an N4 sessionestablishment response message corresponding to an N4 sessionestablishment request message that is transmitted to the target UPF bythe SMF when the SMF receives the N11 message from the AMF and decidesto use a new UPF as the target UPF.
 14. The method of claim 11, whereinthe SMF transmits the N4 session modification request message to ananchor UPF when the SMF identifies at least two UPFs, the at least twoUPFs including the anchor UPF.
 15. The method of claim 10, where the SMFreceives, from a source UPF, an N4 session termination response messagecorresponding to an N4 session termination request message transmittedto the source UPF.
 16. The method of claim 10, wherein the at least onestate machine comprises: a mobility management state to complete atleast one of an attachment procedure or tracking area update procedureassociate with a user equipment (UE), the mobility management stateincluding an NMM-DEREGISTERED state and an NMM-REGISTERED state; and aconnection management state to complete an attachment procedureassociated with the UE, the connection management state including anNCM-IDLE state and an NCM-CONNECTED state, and wherein a state machineof the UE is synchronized with the mobility management state and theconnection management state, respectively.
 17. The method of the claim16, wherein the at least one state machine further comprises a sessionmanagement state to complete a signaling connection and at least onebearer connection associated with the UE, the session management stateincluding an NSM-IDLE state, an NSM-READY state, and an NSM-CONNECTEDstate and wherein: a state transition of the AMF from the NSM-IDLE stateto the NSM-CONNECTED state is performed when a new PDU session isestablished upon receipt of a service request message from the UE to theAMF, the SMF being de-selected; a state transition of the UE from theNSM-READY state to the NSM-CONNECTED state is performed when a first PDUsession establishment request message is transmitted to the AMF from theUE, the NSM-CONNECTED state lasting until a last PDU session released;and a state transition of the UE from the NSM-IDLE state to theNSM-READY state is performed when the UE attaches to a network.
 18. Themethod of the claim 17, wherein the NMM-REGISTERED state, theNCM-CONNECTED state, and the NSM-CONNECTED state comprise a radioresource control (RRC) state including an RRC-CONNECTED state and anRRC-IDLE state based on a number of PDU sessions associated with a UEthat comprises the RRC-CONNECTED state, the RRC-IDLE state, and anRRC-INACTIVE state.
 19. A non-transitory computer readable mediumcomprising instructions, that when executed by at least one processor,cause an access and mobility function (AMF) to perform a methodcomprising: determining a state of at least one state machine;receiving, from a target access network (AN), an N2 path switch requestmessage based on the state of the at least one state machine;transmitting, to a session management function (SMF), an N11 message;and transmitting, to the target AN, an N2 path switch requestacknowledgement (Ack) message when receiving an N11 Ack message, fromthe SMF, corresponding to the N11 message, wherein the target ANtransmits a release resource message to a source AN when the target ANreceives the N2 path switch request Ack message.
 20. The non-transitorycomputer readable medium of claim 19, wherein the SMF receives, from auser plane function (UPF), an N4 session modification response messagecorresponding to an N4 session modification request message that istransmitted to the UPF by the SMF when the SMF receives the N11 messagefrom the AMF and decides to reuse the UPF.
 21. The non-transitorycomputer readable medium of claim 19, further comprising program codethat, when executed, causes the AMF to perform transmitting, to at leastone SMF, the N11 message based on a number of packet data unit (PDU)sessions associated with a user equipment (UE).
 22. The non-transitorycomputer readable medium of claim 19, wherein the SMF receives, from atarget UPF, an N4 session establishment response message correspondingto an N4 session establishment request message that is transmitted tothe target UPF by the SMF when the SMF receives the N11 message from theAMF and decides to use a new UPF as the target UPF.
 23. Thenon-transitory computer readable medium of claim 20, wherein the SMFtransmits the N4 session modification request message to an anchor UPFwhen the SMF identifies at least two UPFs, the at least two UPFsincluding the anchor UPF.
 24. The non-transitory computer readablemedium of claim 19, where the SMF receives, from a source UPF, an N4session termination response message corresponding to an N4 sessiontermination request message transmitted to the source UPF.
 25. Thenon-transitory computer readable medium of claim 19, wherein the atleast one state machine comprises: a mobility management state tocomplete at least one of an attachment procedure or tracking area updateprocedure associate with a user equipment (UE), the mobility managementstate including an NMM-DEREGISTERED state and an NMM-REGISTERED state;and a connection management state to complete an attachment procedureassociated with the UE, the connection management state including anNCM-IDLE state and an NCM-CONNECTED state, and wherein a state machineof the UE is synchronized with the mobility management state and theconnection management state, respectively.
 26. The non-transitorycomputer readable medium of the claim 25, wherein the at least one statemachine further comprises a session management state to complete asignaling connection and at least one bearer connection associated withthe UE, the session management state including an NSM-IDLE state, anNSM-READY state, and an NSM-CONNECTED state and wherein: a statetransition of the AMF from the NSM-IDLE state to the NSM-CONNECTED stateis performed when a new PDU session is established upon receipt of aservice request message from the UE to the AMF, the SMF beingde-selected; a state transition of the UE from the NSM-READY state tothe NSM-CONNECTED state is performed when a first PDU sessionestablishment request message is transmitted to the AMF from the UE, theNSM-CONNECTED state lasting until a last PDU session released; and astate transition of the UE from the NSM-IDLE state to the NSM-READYstate is performed when the UE attaches to a network.
 27. Thenon-transitory computer readable medium of the claim 26, wherein theNMM-REGISTERED state, the NCM-CONNECTED state, and the NSM-CONNECTEDstate comprise a radio resource control (RRC) state including anRRC-CONNECTED state and an RRC-IDLE state based on a number of PDUsessions associated with a UE that comprises the RRC-CONNECTED state,the RRC-IDLE state, and an RRC-INACTIVE state.